In vitro inhibition of uropathogenic Escherichia coli biofilm formation by probiotic Lactobacilli isolated from healthy breast fed infants

Biofilm forming Escherichia coli bacterium exhibits multiple drug resistance, which is responsible for recurrent urinary tract infections (UTI) that are difficult to eradicate. The work aimed to investigate the antibacterial and antibiofilm activities of Lactobacilli isolated from faecal microbiota of healthy infants; to identify these isolates and determine their probiotic characteristics. E. coli isolates were recovered from urine samples of patients with urinary tract infections. On the other hand, Lactobacillus isolates were recovered from faeces of breast-fed infants. Five strong biofilm forming E. coli isolates with multidrug resistance (MDR) were selected. The antibacterial potential of Lactobacillus supernatants were assessed via disk diffusion assay. All the tested E. coli isolates showed high susceptibility to the Lactobacillus supernatants; where 54 % of these supernatants expressed inhibition zones diameters ranging from 15- 18 mm. Antibiofilm efficacies of Lactobacillus spp. against E. coli isolates were tested in vitro using microtiter plate assay and scanning electron microscopy (SEM). More than 50 % reduction of biofilms formation by the 5 selected MDR E. coli isolates was observed by most the Lactobacillus isolates. The scanning electron microscopy confirmed the elimination of E. coli biofilms by cells of the Lactobacillus isolates. Preliminary probiotic characteristics of the Lactobacillus isolates were investigated; all isolates tolerated 2 % bile salt concentration and acidic condition at pH 3. Regarding safety of the Lactobacilli for human consumption, all isolates were non hemolytic, and 14 Lactobacillus isolates were sensitive to all tested antibiotics except for vancomycin, as they are naturally resistant to it. About 14 safe probiotic Lactobacillus isolates were identified by API-50 CHL test as; Lactobacillus acidophilus, L. plantarum, L. fermentum and L. paracasei.